Next Row: Purl.Next Row: Follow S1, K1 pattern to and including first p st. Work in pattern across next 8 sts of thumb. Turn. CO 1 st and p across - 9 sts. Turn. CO 1 st - 10 sts.
Work in pattern on these 10 sts to 2 rows less than required thumb length.
K2tog across row.
P2tog on next row.

Cut yarn leaving a tail long enough to run through last sts on needle and sew up seam in thumb. Join yarn by weaving through a few sts on back of mitten so the working end of yarn is next to the thumb section on the right hand side of the mitten.

Pick up 4 sts on the base of the thumb, then continue in pattern across the row.Next Row: P across to the first 2 of the 4 picked up sts, k2tog twice, continue across row. You should now be back to 28 sts.
Continue in pattern until slightly shorter than middle finger.